The present invention relates to an electrode substrate, for a fuel cell of the phosphoric acid type and a process for producing the same, and more in detail, relates to an electrode substrate provided with the manifold, for the fuel cell, comprising (1) the two porous and carbonaceous electrodes respectively provided with the flow channels of the reactant gas and joined to both surfaces of the separator via a flexible graphite sheet, (2) the separator which has been extended beyond the electrode and (3) the manifold which comprises a gas-impermeable and compact carbon plate and is provided with the flow passage for supplying the reactant gas and joined to the thus extended part of the separator via the flexible graphite sheet and the above-mentioned whole composite materials have been formed into one body as carbon, and a process for producing the electrode substrate.
Generally, the substrate as an electrode in a fuel cell of the phosphoric acid type is stacked so that one of the surfaces of the substrate is contacted to the matrix of phosphoric acid and the another surface of the substrate is contacted to the separator.
In addition, in order to form a fuel cell by stacking the electrode substrates, the manifold is disposed on the peripheral (edge) part of the electrode substrate for supplying the reactant gas to the fuel cell to prevent the diffusion of the reactant gas from the side of the electrode substrate to outside at the same time.
Hitherto, in such a fuel cell, the joining of the composite materials thereof to each other has been carried out by using a carbon cement. However, since the carbon cement is eroded by phosphoric acid, there have been the possibilities of causing exfoliation of the composite materials and occurrence of leakage of the reactant gas through the joining part.
Further, there has been a problem from the view point of the mechanical strength of the material that there are occasions of the breaking of such an electrode substrate in handling in the case where the surface area thereof is too large, because an electrode is generally in a thin plate-form.
As a result of the present inventors' studies on the processes for producing the electrode substrate provided with the manifold, for a fuel cell, which does not have the above-mentioned defects, it has been found by the present inventors that the electrode substrate provided with the manifold, for a fuel cell, wherein all the composite materials thereof have been joined by carbon and further calcined to be one body, is particularly excellent in resistance to phosphoric acid, and that since a peripheral part serving also as the gas manifold (hereinafter referred to as the "manifold") has been joined to the peripheral part of the substrate as one body, there is a reinforcing effect thereby and that such an electrode has an excellent handling property. On the basis of their above-mentioned findings, the present inventors have attained the present invention.
Namely, the first object of the present invention is to provide an electrode substrate provided with a manifold, for a fuel cell, wherein the manifold provided with a flow passage for supplying the reactant gas has been formed into one body together with the electrode substrate part as carbon.
The second object of the present invention is provide to an electrode substrate for a fuel cell of the phosphoric acid type, which is excellent in resistance to phosphoric acid.
Other objects and the merits of the present invention will be clear to the persons skilled in the art from the following description.